Pneumatic control device with programmed characteristic, particularly for a vehicle braking device

ABSTRACT

A pneumatic control having programmed characteristic for use especially for a vehicle braking device comprising at least one pilot reducing valve connected to a source of compressed fluid supply, to the atmosphere and to a fluid outlet conduit terminating in a pneumatic control member. The reducing valve has members for controlling the passage of fluid that is operably connected with a programming device that is capable of being corrected by a device for applying different parameters.

United States Patent [191 Lekarski et a1.

[ Mar. 12, 1974 PNEUMATIC CONTROL DEVICE WITH PROGRAMME!)CHARACTERISTIC, PARTICULARLY FOR A VEHICLE BRAKING DEVICE Inventors:Simeon Lekarski, St. Cloud; Pierre Hardy; Leon Hardy, both of Paris, allof France Assignee: Jean Gachot, Enghien1es-Bains,

France Filed: Jan. 4, 1971 Appl. No.: 103,682

Foreign Application Priority Data Aug. 1, 1970 us. Cl. Int. Cl.

France 7000644 91/461, l37/625.66 Fl5b 11/08, F15b 13/042 Field ofSearch 137/625.66, 625.64, 625.6, 137/627.5; 91/457, 454, 461, 469, 304

References Cited UNITED STATES PATENTS Wright, Jr 91/454 X 2,911,00511/1959 Adelson 91/454 X 2,999,513 9/1961 Oetiker 137/627.5 X 3,272,5649/1966 Romaninim. l37/625.66 X

3,277,923 10/1966 Hogelm, 137/627.5 3,536,089 10/1970 Sarbach 137/627.5X 3,601,155 8/1971 Brown 137/625.66

Primary Examiner-Irwin C. Cohen 3 Claims, 16 Drawing Figures PNEUMATICCONTROL MEMBER PATENTEDMAR 12 I974 PNEUMATIC SHEET 1 0F 4 IIIIIII/IAWII5 CONTROL MEMBER FIGS PATENTED A 1 2 191-: 3796; 135

SHEET 2 [IF 4 BRAKING PRESSURE O DECELERATION DECELERATION FATENTED MAR12 1924 sum u or 4 PNEUMATIC CONTROL DEVICE WITH PROGRAMMEDCHARACTERISTIC, PARTICULARLY FOR A VEHICLE BRAKING DEVICE The presentinvention relates to a pneumatic control device with programmedcharacteristic, particularly for a vehicle-braking device.

For pneumatically controlling different installations and particularlythose which have the same characteristics as a braking device, a controldevice is used which comprises at least one pressure-reducing valve of atype having a large number of advantages over known pressure reducers.

In fact, the reducing valves of known type have a certain number ofdisadvantages, particularly concerning the difficulty in obtaining areducing valve of reduced bulk which is highly accurate and has a highoutput.

Another difficulty resides in the fact that it is sought to reduce thecost of the reducing valve by simplifying its functional components andthis results in insufficient output parameters. Y

Furthermore, the output characteristic of the known reducing valves hasa non-modifyable working, this not permitting them to be adapted to therequirements of the different braking devices for vehicles for whichthey are intended.

In the field of braking, it is also desirable that a reducing valve beconnected to each axle and adapted to the ratios of the braking stress,which must approximate to the best conditions possible.

The reducing valve according to the invention made according to thistechnique enables an apparatus to be obtained which is of extremelyreduced bulk, of simplifled production and of low cost price.

It is therefore possible to associate a pilot' reducing valve acting asprogrammer to another reducing valve of similar design, but enabling amuch higher output power to be had. By this means, the two reducingvalves may be assembled on a common base in order to form an assembly ofconsiderably smaller dimensions than those of the known reducing valves.

Although the reducing valves in the control device according to theinvention are substantially flatter than the known reducing valves,their reaction surfaces are sufficiently large to supply an outputcharacteristic whose precision is at least equal to that of the existingreducing valves, if not greater.

The control device. according to the invention comprises a programmingdevice constituted by plates cut out in order to present a determinedsection and permitting action on the operation of a pilot reducingvalve, in order that it may fulfill the requirements of a controldevice, particularly a braking device. The programming device obtainedby means of sectioned plates may receive means for correcting thecharacteristics according to the load of the vehicle, or means forreducing the braking stress, in the case of locking.

In accordance with the present invention,. the control device comprisesa pilot reducing valve connected respectively to a source of compressedfluid supply, to the atmosphere and to a fluid output conduit ending ina pneumatic control member, said reducing valve comprising members forcontrolling the passage of the fluid, the operation of which isconnected with programming means whose characteristics are capable ofbeing corrected by means for applying different parameters.

The invention will be described in greater detail with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic view showing a pneumatic control device accordingto the invention.

FIG. 2 is a sectional view of a pilot reducing valve.

FIG. 3 is a plan view of the same pilot reducing valve shown in FIG. 2.

FIG. 4 is a sectional view of a reducing valve controlled by a pneumaticsignal.

FIG. 5 is a pneumatic control device applied to a system of braking thetwo axles of a vehicle.

FIG. 6 is a diagram representing the distribution of the braking torqueon two axles of the same vehicle, according to a known load.

FIG. 7 is an embodiment of a control device with braking corrector as afunction of the load of the vehicle.

FIG. 8 is a diagram representing the braking torque of the front axle,as a function of decelerations of the vehicle for different loads.

FIG. 9 is a diagram of the same functions for the rear axle.

FIG. 10 is an embodiment of a braking corrector in the case of apneumatic vehicle suspension.

FIG. 11 is a sectional view, on a larger scale, ofa barrage valve shownon the braking corrector of FIG. 10.

FIGS. 12a to are diagrams representing the correspondence between thedifferent operational pressures.

FIG. 13 is a schematic view of an embodiment of a braking device with asupplementary emergency control.

FIG. 14 is a schematic view of an embodiment of a braking control devicewith anti-locking device.

Referring now to the drawings, FIG. 1 shows an embodiment of a controldevice according to the invention, which comprises a pilot reducingvalve 1 connected respectively by a conduit 2 to a source of pressurisedfluid 3, by a conduit 4 for the reaction return and by a fluid outputconduit 5 to a high outlet reducing valve 6 which is itself connected bya conduit 7 to the source of pressurised fluid 3, by a conduit 8 for thereaction return and finally by a fluid output conduit 9 to a pneumaticcontrol member 9', particularly a pneumatic jack for controlling abraking member of a vehicle.

The pilot reducing valve 1 comprises a control member 10 connected toprogramming means making it possible to control the passage of the fluidcoming from the source 3 and directed towards the high outlet reducingvalve 6 which feeds the pneumatic control member and actuates thislatter according to a determined program.

FIGS. 2 and 3 show an embodiment of a pilot reducing valve 1 whichcomprises a rigid stamped plate 11 and a rigid plate 12 between whichare arranged two flat elements are elastic layers 13, 14; above therigid layer 12 are arranged two diaphragms 15 and 16 which are heldtightened on the plate by an intermediary member 17 and an end member18.

The more rigid central parts 19 and 20 of the diaphragms 15 and 16 areextended by bosses 21, 22 which are used for transmitting the forcesexerted on the different members of the reducing valve.

The rigid plate 11 has a stamped enclosure 23 which is closed by theelastic layer 14 which has a central aperture 24 normally obturated bythe boss 22 of the diaphragm 16 which traverses the rigid plate 12 andthe elastic layer 13. Furthermore, the elastic layer 13 has a conduit 25in communication with the atmosphere.

In the members 17, 18, the membranes 15, 16, the rigid plate 12 and theelastic layer 13, there is provided a conduit 26 which terminates on oneside beneath the diaphragm l6 and may be placed in communication withthe enclosure 23.

Beneath the most rigid central part 19 of the diaphragm is arranged oneof the ends of two leaf springs 27, 27a, the other end of which is fixedbetween the body 16 and a stop 28 by means of a shaft 29, said springs27, 27a being displaceable by means of a movable support member 30 whichslides in the space 31 whilst abutting on the body 17; the movablesupport member 30 is unitary with a slide 32 having a slot 33 in whichis engaged the sectioned end 34 of a plate 35 acting on the slide 32 inopposition to a spring 36. On the other hand, the diaphragm 15 issubjected in its upper central part to the action of a helical spring37.

The pilot reducing valve operates in the following manner. 4

The compressed fluid coming from the source 3 is directed by the conduit2 (FIG. 1) towards the enclosure .23 through an aperture (not shown inthe drawing).

Initially, the springs 27, 27a and the movable support member arelocated in the position shown in FIGS. 2 and 3 for which no action isexerted on said springs.

. In this case, the pressurised fluid acts on the boss 22 of thediaphragm l6, repelling said latter in the direction of the boss 21 ofthe diaphragm 15, the pressure exerted by the compressed fluid on thislatter being however lower than that of the helical spring 37, thisresulting in the elastic layer 14 remaining in tight contact with theboss 22, acting as valve and preventing passage of the compressed fluidby the aperture 24.

Whilst the plate 35 is being displaced in the direction of'arrow A, itsengagement in the slot 33 causes the displacement of the movable supportmember 30 in the space 31, and positions the member 30 for the springs27, 27a. When the member 30 draws near the central axis of the diaphragm15, the stiffness of the springs 27, 27a increases, and consequently theforce of the springs directed towards the diaphragm 15 to lift it alsoincreases. If the displacement of the support member 30 is reversed, theeffect on the diaphragm 15 is also reversed.

As the boss 21 is itself lifted, the pressurised fluid of the chamber 23acts on the boss 22 of the diaphragm 16 in order to lift said latter.The elastic layer 14 also lifts until it reaches the elastic layer 13against which it is stoppedBy this means, a clearance is obtainedbetween the rigid plate 12 and the boss 22, so that the compressed fluidpasses between the rigid plate 12 and beneath the diaphragm 16, thecavity 38 provided in the body 17 enabling the diaphragm 16 to take theform of this cavity.

In this way. it is therefore possible to establish communication betweenthe enclosure 23 and the conduit 26, by the aperture 24, the spacebetween the plate 12 and the boss 22, and the passage beneath thediaphragm 16.

Simultaneously, the difference in pressure between the compressed fluidand the atmosphere holds the layer 14 against the layer 13, thuspreventing the escape of the compressed fluid towards the aperture 25and towards the atmosphere, the layers 13 and 14 acting as retainingvalve.

The compressed fluid located in the output conduit 26 communicates withthe reaction chamber 39 located above the diaphragm 15 by the calibratedconduit 40. The pressure of the fluid increasing in the chamber 39actuates the diaphragm 15 in the direction of the diaphragm 16 untilequilibrium is established between the action of the pressure of thefluid and that of the springs 27, 27a.

At the outlet aperture of the conduit 26, a constant pressure of thefluid is established.

In the case where the pressure of the fluid is maintained in the outletconduit 26 and where the pressure of the springs 27,2711 on the centralpart 19 of the membrane 15 decreases, thereaction stress developed bythe fluid pressure at the outlet on the diaphragm 15 becomes dominantand the movable partof the diaphragms moves towards the diaphragm 16whose boss 22 abuts on the elastic layer 14 and breaks the seal betweenthe layers 13 and 14, thus placing in communication the outlet conduit26 and the atmopshere by conduit 25.

The escape to the atmosphere of the fluid located in the outlet conduit26 is effected up to the moment when the equilibrium is againestablished between the reactions on the diaphragm 15 and the stressesof the springs 27, 27a.

This pilot reducing valve 1 with variable characteristics must havereduced fluid passages and it cannot be used alone in particular foractuating the cylinders of a braking device which necessitate aconsiderable output of fluid.

To this end, the control device according to the invention comprises incombination with the pilot reducing valve 1, a high outlet reducingvalve 6 (FIGS. 1 and 4) which is made substantially in the same manneras the reducing valve 1.

The difference between thesetwo valves resides in the fact that in thehigh outlet reducing valve (FIG. 4), the chamber 41 located between thediaphragms l5 and 16 is sealed and it is connected, by a conduit 42, tothe conduit 5 through which the control pulses emitted by the pilotreducing valve I arrive.

Consequently, the members for controlling the programmation 30, 35 and32 and the leaf springs 27, 27a which were present in'the reducing valve1 are eliminated.

The principle of operation of the high outlet reducing valve 6 issubstantially the same as the pilot reducing valve 1.

The action of the leaf springs 27, 27a on the diaphragm 15 is replacedin the reducing valve 6 by the action of the pressurised fluid emittinga control signal and acting on the diaphragm 15. The surfaces of thecentral parts 19, 20, of the diaphragms are very different in order toensure the necessary amplification of the reaction coming from theconduit 40 and to obtain a high precision of the reducing valve.

The control device described hereinabove may be applied moreparticularly to a vehicle braking device as shown in FIG. 5.

This braking device enables different braking pressures to be obtainedon the two axles, said pressures varying according to two distinct lawswhich are as close as possible to ideal conditions.

This braking device comprises two control assemblies referenced a and b,such as that shown in FIG. 1, the programming plates 35a, 35b beingarticulated by means of an axis 46 to-a control member 45 unitary with abrake pedal (not shown in the drawing) at the disposal of the driver ofthevehicle.

The high outlet reducing valves 6a and 6b respectively ensure the feedof the brake cylinders of the front and rear axles of the vehicle.

On the diagram of FIG..6, the abscissa 0x represents the groundadherence (deceleration) and the ordinate 0y the braking pressure(braking torque), the curves 43 and 44 corresponding respectively to theideal distribution curves of the braking torque for the front and rearaxles which are often used by vehicle constructors.

By means of relatively simple mathematical or graphic methods, it ispossible to determine the form of the sections 34a, 34b of the plates35a, 35b so that for a given position of the brake pedal unitary withthe control member 45, a corresponding position of the plates 35a, 35bis obtained which determine the fluid pressures at the outlet of thereducing valves 6a 6b which correspond to the pressures shown on curves43, 44 of FIG. 6.

By this means, the braking control device of each type of vehicle may beadapted to the requirements thereof and enables a good distribution ofthe braking to be obtained by simply replacing the programming members,particularly the plates 35a, 35b.

Furthermore, it may be necessary to modify the braking force accordingto the load of the vehicle and FIGS. 8 and 9 show diagrams on which theabscissa 0x represents the deceleration and the ordinate 0y the brakingpressures.

The curves 47 and 48 of FIG; 8 respectively represent the braking torquewith loaded vehicle and with no load for the front axle and the'curves49 and' 50 the braking torque for loaded and non-loaded rear axle.

This modification of the braking force is obtained by means of brakingcorrectors. The control shown in FIG. 7 comprises means enabling thecharacteristics of a pilot reducing valve to be modified in order toobtain a braking corrector.

In the case of a vehicle comprising a mechanical spring suspension (FIG.7), the distance between the bodywork and the axles which variesaccording to the load, may be controlled by means including a punchedcard 51 with three columns 53a, 53b 53c fixed to the bodywork 52 and apneumatic pickup 54 corresponding to each column 53a, 53b, 53c,'is fixedto the axle envisaged 56 and fed by a source of pressurised fluid.

It is therefore possible to obtain a certain combination of signalscorresponding to the different levels of the bodywork of the vehicle.

The level line V which corresponds to the vehicle which is not loaded,indicates that for this level, the card 51 has no perforation, whilstthe line C corresponding to the loaded vehicle indicates that for thisdevice level the card 51 has three perforations 53a, 53b and 530.

These signals control three cells 57a, 57b, 570, having the logic NOfunction which are connected to their outlet with the cylinders 58a,58b, 586 of jacks.

The jacks may be connected in series so that, the three jacks beingunder pressure on the outlet, a stroke is obtained which is equal to thesum of the strokes of pistons 59a, 59b, 590.

This last piston 590 controls the position of a stop member 60 againstthe action of a spring 61 in abutment on a fixed stop member 62.

The stop member 60' is capable of abutting against the face 63 of theplate 35 which is opposite the sectioned face 34.

The control device comprises, as in the preceding embodiments, aprogramming plate 35 for controlling a pilot reducing valve 1 associatedwith a high outlet reducing valve 6.

When the vehicle is'loaded, the punched card 51 is in a low positioncorresponding to the level C and in this case the columns 53a, 53b, 530have three apertures on a line, enabling a low level signal to beobtained from pick-ups 54 and a high level signal at the outlet of theNO cells 57a, 57b, 570.

The cylinders 58a, 58b, 58c are fed with pressurised fluid and the stopmember 60 is located in the position shown in FIG. 7. When the brakepedal is actuated, the plates 35 are driven in the direction of arrow Aand by reason of its opposite sectioned faces 34 and 63, there resultmodifications of the elasticity of the flat springs 27, 27a equal to thesum of the displacements defined by the sectionsof said faces, said sumvarying according to the position of the plates in question.

Particularly for the position indicated in FIG. 7 of the stop member 60,the displacement is maximum and the pressures of the fluid at the outletof the two pressure reducers 1 and 6 corresponds to the full load curves47 and 49 of FIGS. 8, 9.

When the vehicle is not loaded, the pickups are located opposite theline V and the cylinders 58a 58b, 58c are not fed with fluid, the stopmember 60 is then located in a leftward limiting position and is nolonger in contact with the sectioned plate 35 which is then guided bythe support member 64.

It is thus possible to obtain, by means of three cylinders having anidentical stroke, different braking characteristics as a function of theload of the vehicle. Where the cylinders used have different strokes, itis possible to obtain, by their combination, ten different brakingcharacteristics.

As the operational safety of the device is obtained by the use of NOcells, if for any reason one of the pickups determining the load did notoperate correctly, its break-down is manifested by an absence of controltowards the NO cell which continues to emit a signal to its outlet. Ifall the pick-upsdid not operate at the 7 lays with pushes directlyfeeding the cylinders 58a, 58b, 580.

The cylinders 58a, 58b, 58c having different strokes may be arranged inparallel and not in series.

According to another embodiment, it is possible to provide two punchedcards, one of which being for the front axle, the other for the rearaxle, said cards enabling the braking pressures to be corrected as afunction of the dynamic distribution of the load, according to thedifferent decelerations.

According to another embodiment, it is possible to make the stop member60 operate directly by means of a mechanical device, converting thedisplacement of the chassis into a displacement of the stop member.

In the case of a pneumatic suspension device (FIGS. 10 and 11)comprising pneumatic cushions 65, it is possible to use the elasticlayer 66.of the cushion for constituting barrage valves 67 which areconnected on the one hand to a source of pressurised fluid 68 and on theother hand to a calibrated escape aperture 69 and to a cell with logicfunction 57a terminating in a control cylinder 58a as in the deviceshown in FIG. 7.

FIG. 11 shows in section a barrage valve 67 made on a pneumatic cushion65 inflated to an inner pressure Pc which varies according to the loadof the vehicle.

Around the cushion is disposed a metal belt 70 in which is made, bystamping, an enclosure 71 whose width is equal to d. There are welded tothe belt 70 two bosses 72, 73 which have a conduit 74 for the inlet (pa)and the outlet of the fluid (Ps) in the enclosure 71, through apertures75 provided in the wall 70 of the belt.

For a determined value of the width d of the enclosure and of the innerpressure Pc of the pneumatic cushion, a predetermined opening pressureis obtained.

The correspondence between the opening pressure and the'feed pressurefor three distinct valves with different widths d is shown in thediagram of FIG. 12a in which:

d1 d2 d3 and Pc constant P0 3.

The arrow F indicates the direction of the increase of Pa and arrow F2indicates the direction of decrease of Pa. The highest opening pressurecorresponds to the smallest distance d3.

The diagram of FIG. 12b shows the influence of the pressure Pc of thecushion 65 on the opening pressure PS for a valve comprising anenclosure 71 of predetermined width d. In this case, Pcl P02 P03 and thedistance d is equal to d3.

The diagram of FIG. 12c shows the operation of the three barrage valves67 mounted on a suspension cushion which supports a variable load.

For the smallest pressure Pa in the cushion 65 (nonloaded vehicle), thethree barrage valves 67 are open, the three NO cells 57a, 57b, 57c areclosed and the pistons 59a, 59b 59c of the cylinders 58a, 58b, 580 arein withdrawn position.

With the increase in pressure Pc, the successive closures are obtained:of the valve 67 comprising the smallest width d3, followed by the valveof width d2 and lastly the valve of width d1. In this way, when thevehicle is fully loaded, all the valves are closed and the three outputsignals Ps escape through the calibrated apertures 69 so that thepistons 59a, 59b, 590 of the cylinders 58a, 58b, 58c are in outletposition.

provide a conversion of the load on the axle into an electric signalby-piezo-electrical pickup and the conversion of this electric signalinto a pneumatic signal, in order to control the pistons 59a, 59b, 590of the cylinders 58a, 58b,58c or the direct use of the electric signalby an electro-mechanical device which directly controls the stop members60.

FIG 13 shows a braking device which, in addition to controlling thebraking 'of the front and rear axles, as shown in FIG. 5, comprising anemergency braking control.

As in the braking device described hereinabove, a pedal 76 is connectedto a control member 45 on which are articulated by means of an axis 46programming plates 35a, 35b, 350 which respectively control pilotreducing valves la, 1b, 1c and high outlet reducing valves 6a, 6b, 6c.The pressure reducer 6a feeds the cylinders 77 of the rear brakes,pressure reducer 6b feeds the cylinders 78 of the front brakes andpressure reducer 6c the cylinders 79 of the emergency brake.

In the case of a breakdown of the main braking device (a, b), the safetydevice may be put into operation manually by a switch 80 located on thedashboard, or a switch 81 actuated by the pedal 76 at the end of itsstroke.

The switches 80 and 81 may be either electric or pneumatic, operating asrelays with memory functions which change their state after eachcontrol. By this means, the operation of the safety device may bemaintained up to the cancellation signal which occurs following a newoperation of one of the switches,

The switches 80 and 81 are connected to a control member 82 of pneumaticor electromechanical type which acts against a spring 83 on a stopmember 84, capable of abutting against the blade 350 in order to rendersaid latter operative for the control of the pilot reducing valve 10 andof the reducing valve 60 which feeds the cylinder 79 of the emergencybrake.

By this means, an emergency control is had with programmed brakingcharacteristics and use is made of the emergency brake device onlyoutside normal operation of the main braking device, thus limiting therisks of simultaneous wear of the two circuits.

According to another embodiment shown in FIG. 14, the control device isprovided with a locking detector 85 which is connected to a controlmember 86 acting against a spring 87 which maintains the stop member 88in contact with the face of a programming plate 35 which is opposite thesectioned face 34.

When the signal coming from the locking detector is applied to the stopmember 88, the plate 35 moves back whilst reducing the pressure of thefluid at the outlet of the pilot pressure reducer and by means of thehigh outlet pressure reducer, also reduces the pressure in the brakecylinders.

What we claim is: v

1. A pneumatic control device with programmed characteristics,particularly for a vehicle braking device, comprising a pneumaticcontrol member, at least one pilot reducing valve consisting of astacking of first and second rigid plates and first and second layers ofelastic material, said first of said rigid plates having an enclosuredelimited by said first elastic layer which is in contact with saidsecond elastic layer, said second elastic layer having an aperture'incommunication with the atmosphere and abutting against said second rigidplate, a source of compressed fluid, means connecting the enclosure tosaid source of compressed fluid, a first diaphragm disposed to overliesaid second rigid plate and having a boss thereon, said first elasticlayer having a central aperture which is normally obturated by said bossof said first diaphragm, a second diaphragm having a boss thereon anddisposed above said first diaphragm, a fluid outlet conduit in saidpilot reducing valve, the central aperture in said first elastic layerbeing capable of connection to said fluid outlet conduit by a spacedelimited between said second rigid plate and said first diaphragm, whenthis later is lifted under the action of said boss of said seconddiaphragm, means defining a chamber above said second diaphragm andbeing in communication with said fluid outlet conduit, a helical springdisposed in said chamber, said second diaphragm being normallymaintained in contact with said diaphragm by the action of said he licalspring, two leaf springs having first ends fixed to the casing of saidpilot reducing valve and which, at their opposite ends, are in abutmentwith said second diaphragm, a spring loaded movable member, having anaperture therein, associated with said leaf springs and adapted todisplace said leaf springs during movement thereof, the movement of saidmovable member being controlled by programming means, a high outletreducing valve having inlet and outlet sections, the inlet section ofsaid high outlet reducing valve being connected to said fluid outletconduit of said pilot reducing valve and to the source of compressedfluid and said outlet section being connected to said pneumatic controlmember.

2. A control device of claim 1, wherein said first and second diaphragmshave different surfaces superposed for controlling said first and secondelastic layers.

3. The control device of claim 1, wherein said programming meanscomprises a control member, a sectional plate pivotably mounted at oneof its ends on said control member having a section whose shapedetermines the operational program of said pilot reducing valve, saidother end engaging in said aperture of said sliding control member, saidmovable member acting when urged by said other end of said sectionalplate, on said leaf springs which in turn act by flexing on said boss ofsaid second diaphragm of said pilot reducing valve.

member, the other end of said control

1. A pneumatic control device with programmed characteristics,particularly for a vehicle braking device, comprising a pneumaticcontrol member, at least one pilot reducing valve consisting of astacking of first and second rigid plates and first and second layers ofelastic material, said first of said rigid plates having an enclosuredelimited by said first elastic layer which is in contact with saidsecond elastic layer, said second elastic layer having an aperture incommunication with the atmosphere and abutting against said second rigidplate, a source of compressed fluid, means connecting the enclosure tosaid source of compressed fluid, A first diaphragm disposed to overliesaid second rigid plate and having a boss thereon, said first elasticlayer having a central aperture which is normally obturated by said bossof said first diaphragm, a second diaphragm having a boss thereon anddisposed above said first diaphragm, a fluid outlet conduit in saidpilot reducing valve, the central aperture in said first elastic layerbeing capable of connection to said fluid outlet conduit by a spacedelimited between said second rigid plate and said first diaphragm, whenthis later is lifted under the action of said boss of said seconddiaphragm, means defining a chamber above said second diaphragm andbeing in communication with said fluid outlet conduit, a helical springdisposed in said chamber, said second diaphragm being normallymaintained in contact with said diaphragm by the action of said helicalspring, two leaf springs having first ends fixed to the casing of saidpilot reducing valve and which, at their opposite ends, are in abutmentwith said second diaphragm, a spring loaded movable member, having anaperture therein, associated with said leaf springs and adapted todisplace said leaf springs during movement thereof, the movement of saidmovable member being controlled by programming means, a high outletreducing valve having inlet and outlet sections, the inlet section ofsaid high outlet reducing valve being connected to said fluid outletconduit of said pilot reducing valve and to the source of compressedfluid and said outlet section being connected to said pneumatic controlmember.
 2. A control device of claim 1, wherein said first and seconddiaphragms have different surfaces superposed for controlling said firstand second elastic layers.
 3. The control device of claim 1, whereinsaid programming means comprises a control member, a sectional platepivotably mounted at one of its ends on said control member, the otherend of said control member having a section whose shape determines theoperational program of said pilot reducing valve, said other endengaging in said aperture of said sliding control member, said movablemember acting when urged by said other end of said sectional plate, onsaid leaf springs which in turn act by flexing on said boss of saidsecond diaphragm of said pilot reducing valve.